Competition for competition’s sake isn’t going to make the App Store better, it’s just going to cause fragmentation. Epic for example - there is nothing short of Apple giving them the ability to setup their own App Store, keep all the profits and maintain their own privacy rules, etc., that will make them happy. They see how much money Apple makes and they want it.
The issue shouldn’t be what is good/bad for Epic, Apple, Facebook or whoever. It needs to come down to what is good for the user. Having ten different app stores, with different rules to appease companies that want to squeeze every dollar (both literally and through personal information) that they can out of users isn’t what’s best.
Apple shouldn’t be allowed to screw over companies, but at the same time they are the platform owner and need to be allowed to create the rules of said platform. It’s like you said, if people don’t like it, they will leave Apple and get other phones and that is just the market at work.